'The Sing Off' on NBC is unlike any other vocal competition on TV because the contestants only use their voices.  There's no background music, no instruments, it's all acapella. 

This week its Classic Rock & Country night.  The 6 groups left will blend one rock and one country song and the group Urban Method is taking on Carrie Underwood's 'Before He Cheats.'  Their fate lies in the hands of the judges, Ben Folds, Sara Bareilles and Shawn Stockman of Boys II Men.  America gets to choose the winner though, when online voting begins November 21st.  They'll get $200,000 and a Sony recording contract.  The winner will be crowned November 28th.

Tune in to NBC at 8 to hear all the talent go country.  Listen to Urban Method's version of Carrie Underwood's 'Before He Cheats' below.